Car battery voltage vs state of charge definition,used hybrid batteries for sale uk,laptop batteries gauteng - Downloads 2016

19.03.2015
I put together the following chart which indicates the state-of-charge (percent) as it relates to battery voltage or specific gravity. How I determined the voltage values: I researched as many battery manufacturers that I could find regarding their own published SOC data. Note: Voltage measurements are only approximate to determine SOC, and measuring battery voltage is NOT the most accurate way to do this (there are variables under varying circumstances).
Note: For longer battery life, batteries should remain in the green zone (40% or more SOC).
Note: The 100% voltage is NOT the recommended charging voltage (which will be higher, and multi-stage).
If the gravity of each cell stays relatively the same (usually all in the green) does that mean that I don’t need to equalize that battery? The reason I ask is: I have 90 watts of harbor freight panels, run thru a sunsaver controller that charges 2 wally world deep cycle batteries and the gravity has almost never been below the green level, and I never really have had to add much water. My other set up has about 750 watts of poly panels, run through a xantrex 30 amp charge controller charging a trojan 12 volt golf cart battery. I guess my question is do I need to do this since the wally world batteries always seem to be in good shape as per hydrometer readings? I built an off-grid system for my home and have expanded and maintained it myself over the years, so that is my knowledge base.
Also, NEVER combine different types, or age, or widely differing state of charge of your batteries when charging. Thanks Carl, and as you insinuated, there are variables, including temperature compensation measurements and others. Saw this as I was looking for a SG to SOC chart and thought I would make a couple of comments.
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The links below are on this page - you can also just scroll down if you want to read them all. A printable version of this page will be available in Adobe PDF format when we finish updating this page for downloading and printing: Most of the charts have small images for faster downloading. Although Alessandro Volta in Italy is usually credited with being the inventor of the modern battery (Silver-Zinc), ancient cells have been discovered in Sumerian ruins, origin around 250 BC.
Batteries were re-discovered much later by Alessandro Volta after which the unit of electrical potential was named, the volt. Common use of the word, "battery" in electrical terms, is limited to an electrochemical device that converts chemical energy into electricity, by a galvanic cell. Part - or most - of the loss in charging and discharging batteries is due to internal resistance. Typical efficiency in a lead-acid battery is 85-95%, in alkaline and NiCad battery it is about 65%. Practically all batteries used in PV and all but the smallest backup systems are Lead-Acid type batteries. We have had almost no direct experience with the NiFe (alkaline) batteries, but from what we have learned from others we do not not recommend them - one major disadvantage is that there is a large voltage difference between the fully charged and discharged state.
An important fact is that ALL of the batteries commonly used in deep cycle applications are Lead-Acid. Batteries are divided in two ways, by application (what they are used for) and construction (how they are built). Flooded may be standard, with removable caps, or the so-called "maintenance free" (that means they are designed to die one week after the warranty runs out). The lifespan of a deep cycle battery will vary considerably with how it is used, how it is maintained and charged, temperature, and other factors. These are some typical (minimum - maximum) typical expectations for batteries if used in deep cycle service. Starting (sometimes called SLI, for starting, lighting, ignition) batteries are commonly used to start and run engines.
There is generally no problem with this, providing that allowance is made for the lower cranking amps compared to a similar size starting battery.
It will not hurt a deep cycle battery to be used as a starting battery, but for the same size battery they cannot supply as much cranking amps as a regular starting battery and is usually much more expensive. Sometimes called "fork lift", "traction" or "stationary" batteries, are used where power is needed over a longer period of time, and are designed to be "deep cycled", or discharged down as low as 20% of full charge (80% DOD, or Depth of Discharge).
Plate thickness (of the Positive plate) matters because of a factor called "positive grid corrosion".
Most industrial (fork lift) deep-cycle batteries use Lead-Antimony plates rather than the Lead-Calcium used in AGM or gelled deep-cycle batteries and in automotive starting batteries. Lead-Antimony (such as forklift and floor scrubber) batteries have a much higher self-discharge rate (2-10% per week) than Lead or Lead-Calcium (1-5% per month), but the Antimony improves the mechanical strength of the plates, which is an important factor in electric vehicles. Gelled batteries, or "Gel Cells" contain acid that has been "gelled" by the addition of Silica Gel, turning the acid into a solid mass that looks like gooey Jell-O. Since all the electrolyte (acid) is contained in the glass mats, they cannot spill, even if broken.
Nearly all AGM batteries are "recombinant" - what that means is that the Oxygen and Hydrogen recombine INSIDE the battery. The charging voltages are the same as for any standard battery - no need for any special adjustments or problems with incompatible chargers or charge controls.
AGM's do not have any liquid to spill, and even under severe overcharge conditions hydrogen emission is far below the 4% max specified for aircraft and enclosed spaces. Even with all the advantages listed above, there is still a place for the standard flooded deep cycle battery. Battery capacity (how many amp-hours it can hold) is reduced as temperature goes down, and increased as temperature goes up. Thermal mass means that because they have so much mass, they will change internal temperature much slower than the surrounding air temperature. Even though battery capacity at high temperatures is higher,  battery life is shortened. One last note on temperatures - in some places that have extremely cold or hot conditions, batteries may be sold locally that are NOT standard electrolyte (acid) strengths. A battery can meet the voltage tests for being at full charge, yet be much lower than it's original capacity. On the table below, you have to be careful that you are not just measuring the surface charge.
Let’s face it, since us Toy Hauler owners mostly dry camp, our batteries are extremely important. The life of your deep cycle batteries will largely be affected by how it’s used and how it’s maintained. How a battery is used is probably the single most important factor on how long a battery will last. Most experts agree that you don’t want to let your battery’s state of charge get below 50%.
To measure the depth of discharge and other important metrics like current voltage, consumed amp hours, and time remaining, you may want to invest in a good digital battery monitor like the LinkPRO from Xantrex. Good battery maintenance includes making sure the water level never gets below the top of the lead plates.
Subscribe to RSS or enter you email to receive newsletter for news, articles, and updates about what's new. To obtain maximum service life and capacity, along with acceptable recharge time and economy, constant voltage-current limited charging is recommended. As a result of too high a charge voltage excessive current will flow into the battery, after reaching full charge, causing decomposition of water in the electrolyte and premature aging.
If too low a charge voltage is applied, the current flow will essentially stop before the battery is fully charged.
Batteries which are stored in a discharge state, or left on the shelf for too long, may initially appear to be “open circuited” or will accept far less current than normal.
Conversely for Gel batteries fitted close to the alternator (under-bonnet with a thick gauge cabling) there is a real risk of damage due to over-charging as the alternator output can be too high for the battery.
Many Portable Generators do not have battery charging circuitry built-in and should be used with care if they provide a DC outlet (although you could plug a battery charger into the 240V socket, it seems a fairly inefficient way to operate). The later models (from Honda et al) with the built in chargers can provide a reasonably quick and efficient battery top-up on sites where they are allowed (or when off-site), although some users do grow tired of the noise and migrate to solar over time. Part – or most – of the loss in charging and discharging batteries is due to internal resistance. Gelled batteries, or “Gel Cells” contain acid that has been “gelled” by the addition of Silica Gel, turning the acid into a solid mass that looks like gooey Jell-O.
Deep cycle batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates. Unfortunately, it is often impossible to tell what you are really buying in some of the discount stores or places that specialize in automotive batteries. Marine batteries are usually a “hybrid”, and fall between the starting and deep-cycle batteries, though a few (Rolls-Surrette and Concorde, for example) are true deep cycle. Plate thickness (of the Positive plate) matters because of a factor called “positive grid corrosion”.
The 20-hour rate is the most common for standardising batteries in Australia, while the USA uses a 10-hour rating system.
These are some typical (minimum – maximum) typical expectations for batteries if used in deep cycle service.
An inverter has basically two functions – to provide an alternating current (ac) voltage rather than the direct current (dc) available from the battery, and to raise the voltage up to an average of 240V.
Voltages and Specific Gravity are listed for a 6-volt or 12-volt battery, and battery banks of 24 and 48 volts. Some were slightly different from each-other with regards to their SOC values, however I averaged all of them together to come up with a chart which represents what I believe to be a good general indication. A more accurate method is to measure the specific gravity of each cell within the battery, however for many batteries this is difficult or impossible (AGM batteries, for example). Occasional dips into the yellow may not be harmful, but continual discharges to those levels will shorten battery life considerably.
Just thought it might be helpful to add that one tool I’ve found useful is the little floating balls thing for checking individual cell status in lead acid batteries. I mainly use this system for 12 volt water pumps,a few LED’s and cfl lights and occasionally power tools. My immediate thought about the differences in your two battery banks is that the wally world batteries are newer, or less heavily used than the Trojan.
I do off grid solar for a living, 25 years now and I sent a customer the link to this chart to give him an extra tool to keep tabs of his system.
Due to the high volume of emails going out and some service providers blocking them as spam, users have either been getting them late, or not at all. Batteries that are being charged will be higher - the voltages while under charge will not tell you the state of charge, you have to let the battery sit for a atleast 3hours.To get the correct state of charge voltage.
All we have room for here is a basic overview of batteries commonly used with photovoltaic power systems. The jar was found in Khujut Rabu just outside Baghdad and is composed of a clay jar with a stopper made of asphalt. A rock, pushed to the top of a hill, can be considered a kind of battery, since the energy used to push it up the hill (chemical energy, from muscles or combustion engines) is converted and stored as potential kinetic energy at the top of the hill.
A galvanic cell is a fairly simple device consisting of two electrodes of different metals or metal compounds (an anode and a cathode) and an electrolyte (usually acid, but some are alkaline) solution. Batteries do not make electricity, they store it, just as a water tank stores water for future use.
A battery rated at 180 amp-hours over 6 hours might be rated at 220 AH at the 20-hour rate, and 260 AH at the 48-hour rate. True deep cycle AGM's (such as Concorde) can approach 98% under optimum conditions, but those conditions are seldom found so you should figure as a general rule about a 10% to 20% total power loss when sizing batteries and battery banks. Another problem is that they are very inefficient - you lose from 30-40% in heat just in charging and discharging them. In extreme cases, it can vary to extremes - we have seen L-16's killed in less than a year by severe overcharging and water loss, and we have a large set of surplus telephone batteries that sees only occasional (10-15 times per year) heavy service that were just replace after 35+ years.
There are so many variables, such as depth of discharge, maintenance, temperature, how often and how deep cycled, etc. These are usually special purpose "float service", but often appear on the surplus market as "deep cycle". As a general rule, if you are going to use a true deep cycle battery (such as the Concorde SunXtender) also as a starting battery, it should be oversized about 20% compared to the existing or recommended starting battery group size to get the same cranking amps.
These are often called traction batteries because of their widespread use in forklifts, golf carts, and floor sweepers (from which we get the "GC" and "FS" series of battery sizes). The advantage of these batteries is that it is impossible to spill acid even if they are broken.
If overcharged, voids can develop in the gel which will never heal, causing a loss in battery capacity. These use gas phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis.
And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents.
This means that they can sit in storage for much longer periods without charging than standard batteries.


The plates in AGM's are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery.
This is why your car battery dies on a cold winter morning, even though it worked fine the previous afternoon. A large insulated battery bank may vary as little as 10 degrees over 24 hours internally, even though the air temperature varies from 20 to 70 degrees. Battery capacity is reduced by 50% at -22 degrees F - but battery LIFE increases by about 60%. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD.
Lifespan can also be seriously reduced at higher temperatures - most manufacturers state this as a 50% loss in life for every 15 degrees F over a 77 degree cell temperature. This story has been around for 100 years, and originated back when battery cases were made up of wood and asphalt. This will NOT tell you how good (capacity in AH) the battery condition is - only a sustainedload test can do that. To properly check the voltages, the battery should sit at rest for a few hours, or you should put a small load on it, such as a small automotive bulb, for a few minutes. Following are some tips I’ve picked up over the years along with some products I think are worth a look.
This is typically measured in the number of deep discharges and the average depth of each discharge.
The LinkPro can also be programmed to automatically start your generator when your batteries get to a pre-set limit. Since battery compartments are dark and usually cramped, I found the best way to accomplish this is to get an automatic watering system like the Pro-Fill system by Flow-Rite. Once hooked up all you need to do is pump distilled water from a jug with the included hand pump.
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As the battery reaches full charge, the positive plate begins generating dioxide causing a sudden rise in voltage due to decreasing internal resistance. This allows some of the lead sulfate to remain on the electrodes, which will eventually reduce capacity. They are not battery chargers however, and will never fully charge a Deep Cycle battery, so it’s best to use a battery charger when main power is available to top up the battery charge and avoid reduced battery life from sulphation. It is for this reason that we highly recommend NOT using GEL batteries with car alternators. A battery rated at 180 amp-hours over 6 hours might be rated at 220 AH at the 20-hour rate, and 250 AH at the 48-hour rate. The major difference between a true deep cycle battery and others is that the plates are SOLID Lead plates – not sponge. In the hybrid, the plates may be composed of Lead sponge, but it is coarser and heavier than that used in starting batteries.
As a general rule, if you are going to use a true deep cycle battery also as a starting battery, it should be oversized about 20% compared to the existing or recommended starting battery group size to get the same cranking amps. In extreme cases, it can vary to extremes – AGM’s can be killed in less than a year by severe overcharging. These are usually special purpose “float service”, but often appear on the surplus market as “deep cycle”. If a battery has been discharged for some time, or the load was left on indefinitely, it may not readily take a charge. Caution should be exercised to ensure that the charger is disconnected after cycle charging, or that the float voltage is set correctly.
Differences in capacity can cause some batteries to overcharge while others remain undercharged, thus causing premature aging of batteries. To determine the approximate recharge time of a fully discharged battery, divide the battery’s capacity (amp. The difference in characteristics will cause damage to the batteries and possibly to the attached equipment. Measuring and knowing the SOC of a battery or battery bank is useful when applying towards alternative energy, or any other situation where you need to know its condition. Many (most) alt-energy systems incorporate a DC-shunt which keeps track of SOC by monitoring the current flow in and out of the battery or battery bank, which is a very accurate way to track state-of-charge. To be somewhat accurate, the battery should be in that condition for an hour or two before taking a measurement, while for a more accurate measurement you should wait 6 hours up to 24 hours. Generally speaking, the less you discharge the battery before recharge, the longer the battery will last.
The Trojan sounds like it is getting old, and needs more frequent watering and equalizing to keep it functioning. The one thing I would disagree with somewhat from your well written article is concerning the accuracy of state of charge meters.
If you have not received your password reset email please use the password reset function ?forgot password?. Later, that energy is released as kinetic and thermal energy when the rock rolls down the hill. A "Battery" is two or more of those cells in series, although many types of single cells are usually referred to as batteries - such as flashlight batteries. Much of this loss of efficiency is due to higher internal resistance at higher amperage rates - internal resistance is not a constant - kind of like "the more you push, the more it pushes back". A few systems use NiCad, but we do not recommend them except in cases where extremely cold temperatures (-50 F or less) are common.
They all use the same chemistry, although the actual construction of the plates etc varies. Deep-cycle includes solar electric (PV), backup power, traction, and RV and boat "house" batteries. We have seen gelled cells destroyed in one day when overcharged with a large automotive charger. A few Lithium-Ion types are starting to make their appearance, but are much more expensive than Lead-Acid and most charge controllers do not have the correct setpoints for proper charging. The biggest problem with NiFe batteries is that you may have to put in 100 watts to get 70 watts of charge - they are much less efficient than Lead-Acid. The positive (+) plate is what gets eaten away gradually over time, so eventually there is nothing left - it all falls to the bottom as sediment.
The self discharge of batteries with Lead-Antimony plates can be high - as much as 1% per day on an older battery. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage. The Concorde batteries can be almost fully recharged (95% or better) even after 30 days of being totally discharged. In many installations, where the batteries are set in an area where you don't have to worry about fumes or leakage, a standard or industrial deep cycle is a better economic choice. If your batteries spend part of the year shivering in the cold, the reduced capacity has to be taken into account when sizing the system batteries.
For this reason, external (add-on) temperature sensors should be attached to one of the POSITIVE plate terminals, and bundled up a little with some type of insulation on the terminal.
Battery life is reduced at higher temperatures - for every 15 degrees F over 77, battery life is cut in half. However, there are often ratings for other depth of discharge cycles, the most common ones are 10%, 20%, and 50%. This "leakage" or self discharge varies considerably with battery type, age, & temperature.
The acid would leak from them, and form a slow-discharging circuit through the now acid-soaked and conductive floor. This same thing can occur in gelled cells if they are overcharged and gaps or bubbles occur in the gel.
The higher the internal resistance, the higher the losses while charging and discharging, especially at higher currents. A golf cart style battery like the Trojan T-105 will last for about 750 discharge cycles if the average depth of discharge is at 50% of its capacity. And during storage, if possible, keep your rig plugged in so your batteries don’t waste a discharge cycle.
The selection of suitable charging circuits and methods is as important as choosing the right battery for the application.
A constant voltage charge, therefore, allows detection of this voltage increase and thus control of the current charge amount.
Much of this loss of efficiency is due to higher internal resistance at higher amperage rates – internal resistance is not a constant – kind of like “the more you push, the more it pushes back”. The problem is that “golf car” refers to a size of battery (commonly called GC-2, or T-105), not the type or construction – so the quality and construction of a golf car battery can vary considerably – ranging from the cheap off brand with thin plates up the true deep cycle brands, such as Crown, Powersonic, Trojan, etc. It is often hard to tell what you are getting in a “marine” battery, but most are a hybrid. With modern engines with fuel injection and electronic ignition, it generally takes much less battery power to crank and start them, so raw cranking amps is less important than it used to be. The positive (+) plate is what gets eaten away gradually over time, so eventually there is nothing left – it all falls to the bottom as sediment. While plate thickness is not the only factor in how many deep cycles a battery can take before it dies, it is the most important one. Gelled cells batteries can be destroyed in one day when overcharged with a large automotive charger.
The most expensive provide a pure sine wave which is preferred for any sensitive equipment, especially laptops. A 150W unit will handle most camp requirements, but may have trouble starting a laptop (even though the average drain by the computer is much less than this.) A 300W unit is probably a sensible minimum.
To overcome this, leave the charger connected and the battery should eventually begin to accept charge.
Given the right set of circumstances, such as extreme overcharging or shorting of the battery, these gases might vent into the enclosure and create the potential for an explosion when ignited by a spark. It is, therefore, not advisable to mix batteries of different capacities, make, or age in a series string.
Most alternative-energy systems are designed to keep the battery bank at least 50% or higher. When batteries are in series they do not necessarily charge at the same rate and can become imbalanced.
For a very brief discussion on the advantages and disadvantages of these and other types of batteries, such as NiCad, NiFe (Nickel-Iron), etc. Possibly one of the first uses for batteries, although there is some dispute among scholars. When filled with vinegar - or any other electrolytic solution - the jar produces about 1.1 volts.
They are expensive to buy, and very expensive to dispose of due the the hazardous nature of Cadmium. We have seen golf cart batteries destroyed without ever being used in less than a year because they were left sitting in a hot garage or warehouse without being charged. The plates are composed of a Lead "sponge", similar in appearance to a very fine foam sponge. What you save on batteries you will have to make up for by buying a larger solar panel system. They are sometimes used in larger PV systems because you can get a lot of storage in a single (very large and heavy) battery. Thicker plates are directly related to longer life, so other things being equal, the battery with the thickest plates will last the longest.
A new AGM typically self-discharges at about 1-2% per month, while an old one may be as much as 2% per week. If overcharged too many times, some of these batteries can lose enough water that they will die before their time. If left for long periods unused, these should be trickle charged to avoid damage from sulfation - but this applies to ANY battery.
It is for this and other reasons that we no longer sell any of the gelled cells except for replacement use.
AGM batteries main advantages are no maintenance, completely sealed against fumes, Hydrogen, or leakage, non-spilling even if they are broken, and can survive most freezes. Some charge controls have temperature compensation built in (such as Morningstar) - this works fine if the controller is subject to the same temperatures as the batteries.
This holds true for ANY type of Lead-Acid battery, whether sealed, gelled, AGM, industrial or whatever.
You have to be careful when looking at ratings that list how many cycles a battery is rated for unless it also states how far down it is being discharged. Obviously, there are some practical limitations on this - you don't usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. This tends to even out in most systems - they will spend part of their life at higher temperatures, and part at lower. VPC is the volts per individual cell - if you measure more than a .2 volt difference between each cell, you need to equalize, or your batteries are going bad, or they may be sulfated. PD’s 9200 series chargers when combined with their Charge Wizard constantly monitors your batteries voltage and selects the proper mode to safely charge your battery. When temperatures reach 122F battery capacity increases by about 12%, however battery life is shortened. Usually, the battery will start to accept increasing amounts of current until a normal current level is reached. Obviously, there are some practical limitations on this – you don’t usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. These are also called “starved electrolyte”, as the mat is about 95% saturated rather than fully soaked.


The plates are composed of a Lead “sponge”, similar in appearance to a very fine foam sponge. Although these can be cycled down to 20% charge, the best lifespan vs cost method is to keep the average cycle at about 50% discharge.
Starting batteries are usually rated at “CCA”, or cold cranking amps, or “MCA”, Marine cranking amps – the same as “CA”. On the other hand, many cars, boats, and RV’s are more heavily loaded with power sucking “appliances”, such as megawatt stereo systems etc. Golf cart batteries can be destroyed without ever being used in less than a year because they were left sitting in a hot garage without being charged. The cheapest simply provide a square wave ac, which is satisfactory with most motors and some small chargers for cameras, phones etc, but not for most laptop computers.
Bear in mind that Watts = Volts x Amps, so, if we draw the full 300 watts, we will require 25 amps from the 12volt battery, plus 20% to account for inefficiency.
It is set to equalize every 30 days, however sometimes I have to do it more than that, to bring them all back to green. The plates may have become heavily sulfated enough that the equalize mode can’t get it all off into solution.
The equalizing charge ups the charging voltages in order to get enough voltage to the lesser charged batteries in the series chain. Batteries are not 100% efficient - some energy is lost as heat and chemical reactions when charging and discharging. In the past they were often used by railroads as backup power, but nearly all have now changed over to newer types.
AGM batteries are also sometimes called "starved electrolyte" or "dry", because the fiberglass mat is only 95% saturated with Sulfuric acid and there is no excess liquid.
Even the so-called "dry charged" (where you add acid when you need them) have a shelf life of 18 months at most. This gives a very large surface area, but if deep cycled, this sponge will quickly be consumed and fall to the bottom of the cells.
On the other hand, many cars, boats, and RV's are more heavily loaded with power sucking "appliances", such as megawatt stereo systems etc. The negative plate in batteries expands somewhat during discharge, which is why nearly all batteries have separators, such as glass mat or paper, that can be compressed. Most smaller deep cycle batteries (including AGM) use Lead-Calcium plates for increased life, while most industrial and forklift batteries use Lead-Antimony for greater plate strength to withstand shock and vibration. Industrial batteries are usually designated by a part number such as "FS" for floor sweeper, or "GC" for golf cart. They cannot be fast charged on a conventional automotive charger or they may be permanently damaged.
The newer AGM (absorbed glass mat) batteries have all the advantages (and then some) of gelled, with none of the disadvantages. These are also called "starved electrolyte", as the mat is about 95% saturated rather than fully soaked. However, if your batteries are outside, and the controller is inside, it does not work that well. This is actually not as bad as it seems, as the battery will tend to average out the good and bad times.
For example, one of the widely advertised telephone type (float service) batteries have been advertised as having a 20-year life.
Generally, new AGM batteries have the lowest, and old industrial (Lead-Antimony plates) are the highest. Batteries usually go bad for other reasons before reaching this point, but it is something to be aware of if your batteries seem to test OK but lack capacity and go dead very quickly under load. The generally accepted AH rating time period for batteries used in solar electric and backup power systems (and for nearly all deep cycle batteries) is the "20 hour rate".
Therefore, extreme temperatures in either direction are not good for your batteries health. Batteries that are being charged will be higher – the voltages while under charge will not tell you anything, you have to let the battery sit for a while. If there is no response, even to charge voltages above recommended levels, the battery may have been in a discharged state for too long to recover.
The generally accepted AH rating time period for batteries for nearly all deep cycle batteries is the “20 hour rate”. Any battery with the capacity shown in CA or MCA may or may not be a true deep-cycle battery.
The negative plate in batteries expands somewhat during discharge, which is why nearly all batteries have separators, such as glass mat (AGM) that can be compressed. Even the so-called “dry charged” (where you add acid when you need them) have a shelf life of 18 months at most. There are also intermediate types, “modified sine wave”, which combine a number of square waves to approximate a sine wave shape. I combine the batteries whenever we lose power for more than a few hours so we can run TVs, fans DVD player and lights etc. The standard meter for years has been the Tri-Metric meter but I finally gave up on using them because they arent very accurate unless fine-tuned beyond the level most homeowners are capable of understanding. Yes it will over charge the higher charged batteries, which is why the equalizing charge is only applied for a short time, however if the system uses a single battery equalization is not required and can be detrimental.
If you use 1000 watts from a battery, it might take 1050 or 1250 watts or more to fully recharge it.
Automotive batteries will generally fail after 30-150 deep cycles if deep cycled, while they may last for thousands of cycles in normal starting use (2-5% discharge).
However, NiCads can be frozen without damage, so are sometimes used in areas where the temperatures may fall below -50 degrees F. This is not usually a problem with solar electric systems, but if an auxiliary generator or inverter bulk charger is used, current must be limited to the manufacturers specifications. If you look at the fine print, it has that rating only at 5% DOD - it is much less when used in an application where they are cycled deeper on a regular basis. In systems that are continually connected to some type charging source, whether it is solar, wind, or an AC powered charger this is seldom a problem. This can vary with battery types and brands somewhat - when you buy new batteries you should charge them up and let them sit for a while, then take a reference measurement.
This is important because some manufacturers and vendors have chosen to rate their batteries at the 100 hour rate - which makes them look a lot better than they really are.
Batteries that are being charged will be higher - the voltages while under charge will not tell you anything, you have to let the battery sit for a while.
A 10Hr rating is widely used in the USA, therefore many batteries can have 10hr, 20hr or both specifications stated. If you look at the fine print, it has that rating only at 5% DOD – it is much less when used in an application where they are cycled deeper on a regular basis. They are not totally dry – they are actually filled with acid, the plates formed and charged, then the acid is dumped out.
These are usually satisfactory for laptops, but, like the square wave types, often create a lot of radio interference. This will draw from the battery in 1 hour about the same as all other loads discussed above take in a day. You should probably start saving your shekels for a new battery because that one is not going to live much longer. It doesnt help that the manual makes little sense to the layman or that the meter cant read battery voltage and often keeps compounding small errors into bigger ones. It would be wise to buy a desulfator unit for your batteries in order to reverse sulfation of the plates after long periods of less than 100% charge. We have used the Concorde SunXtender AGM batteries in some of our vehicles with no problems. Most AGM batteries will also survive freezing with no problems, even though the output when frozen will be little or nothing. Other standard size codes are 4D & 8D, large industrial batteries, commonly used in solar electric systems. Most better inverters commonly used in solar electric systems can be set to limit charging current to the batteries. Capacity is increased at higher temperatures - at 122 degrees F, battery capacity would be about 12% higher.
It's just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor.
However, one of the biggest killers of batteries is sitting stored in a partly discharged state for a few months. Many batteries are sealed, and hydrometer reading cannot be taken, so you must rely on voltage. This is why most intelligent chargers will have temperature compensation circuitry built in. Occasional dips into the yellow are not harmful, but continual discharges to those levels will shorten battery life considerably. The 20hr rating means that it is discharged down to 10.5 volts over a 20 hour period while the total actual amp-hours it supplies is measured. It’s just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor.
Better inverters commonly used in solar electric systems can be set to limit charging current to the batteries.
The meters that you can get that take their info from the inverter or in the case of Midnite Solar from the charge controller are more accurate because they temperature compensate but they need fine-tuning as well. The major difference between a true deep cycle battery and others is that the plates are SOLID Lead plates - not sponge. For example, most golf cart batteries are rated for about 550 cycles to 50% discharge - which equates to about 2 years. Also, there is an upper limit - a battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%. A "float" trickle charge should be maintained on the batteries even if they are not used (or, especially if they are not used). Hydrometer readings may not tell the whole story, as it takes a while for the acid to get mixed up in wet cells. The 6-hour rate is often used for industrial batteries, as that is a typical daily duty cycle. Sometimes ratings at the 6 hour rate and 100 hour rate are also given for comparison and for different applications. For example, most golf cart batteries are rated for about 550 cycles to 50% discharge – which equates to about 2 years. Also, there is an upper limit – a battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%.
Unfortunately, the only positive way to tell with some batteries is to buy one and cut it open – not much of an option. A 2000W one will provide enough power to run power tools or even an electric jug, but at full output they will draw from the battery about 150-200 amps.
Just yesterday a customer called because his inverter shut down at 23 volts, a definite low battery but the SOC meter claimed he was at 81% full. This happens because at very shallow cycles, the Lead Dioxide tends to build up in clumps on the the positive plates rather in an even film. Even most "dry charged" batteries (those sold without electrolyte so they can be shipped more easily, with acid added later) will deteriorate over time. If measured right after charging, you might see 1.27 at the top of the cell, even though it is much less at the bottom.
Sometimes the 100 hour rate is given just to make the battery look better than it really is, but it is also useful for figuring battery capacity for long-term backup amp-hour requirements. The best determination is to measure the specific gravity, but in many batteries this is difficult or impossible. This happens because at very shallow cycles, the Lead Dioxide tends to build up in clumps on the positive plates rather than an even film. That’s as much current as they winch when fully loaded, and way outside the comfort zone of any deep cycle battery for long periods of time. I sent him a link to your chart and told him to call Magnum tech support to learn to tweak the meter. Sometimes the 100 hour rate is given just to make the battery look better than it really is, but it is also useful for figuring battery capacity for long-term applications like backup, solar, and camping amp-hour requirements. Most 1500w-2000w applications such as microwaves and electric kettles will only run for a few minutes, this will be fine to use with a 100AH+ battery. The chart is for a Concorde Lifeline battery, but all lead-acid batteries will be similar in the shape of the curve, although the number of cycles will vary. The problem is that "golf car" refers to a size of battery case (commonly called GC-2, or T-105), not the type or construction - so the quality and construction of a golf car battery can vary considerably - ranging from the cheap off brand with thin plates up to true deep cycle brands, such as Crown, Deka, Trojan, etc. Marine batteries are usually a "hybrid", and fall between the starting and deep-cycle batteries, though a few (Rolls-Surrette and Concorde, for example) are true deep cycle. It is often hard to tell what you are getting in a "marine" battery, but most are a hybrid. Starting batteries are usually rated at "CCA", or cold cranking amps, or "MCA", Marine cranking amps - the same as "CA". It is sometimes hard to tell, as the term deep cycle is often overused - we have even seen the term "deep cycle" used in automotive starting battery advertising.
Unfortunately, the only positive way to tell with some batteries is to buy one and cut it open - not much of an option.



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